Casing centralizer and mandrel for use in welding large diameter casing

ABSTRACT

A tool for use in welding together large diameter casing sections, particularly in forming liners for deep earth bores. The tool includes fluid pressure actuated expander assemblies operative to align the casing sections, assure concentricity of the sections at the weld joint, and to position an expansible chill ring opposite the weld joint. The tool also includes elements enabling pressure testing the welds, and hydraulic jacking means for moving the tool longitudinally of the casing.

United States Patent Brown [54] CASING CENTRALIZER AND MANDREL FOR USEIN WELDING LARGE DIAMETER CASING [72] Inventor: Cicero C. Brown, c/oBrown Oil Tools,

Inc. P. O. Box 19236, Houston, Tex. 77024 [22] Filed: Oct. 3, 1968 [21]Appl.No.: 764,787

[52] U.S. Cl. ..228/5, 219/60, 228/44, 228/50, 269/104, 285/96 [51] Int.Cl ..B23k 1/20 [58] Field of Search ..228/5,44, 46, 50; 219/60; 269/104;73/495, 49.6; 285/96 [56] References Cited UNITED STATES PATENTS2,l67,896 8/l939 Graham et al. .l ..228/50 2,594,000 4/1952 Elliot..228/ 50 [is] 3,653,573 [451 Apr. 4, 1972 3,261,529 7/1966 Pagan..228/50 3,369,725 2/1968 Thomas et a1. .....228/5O 3,387,761 6/1968Pickard ..228/42 3,458,105 7/1969 Valentine ..228/44 3,461,264 8/1969Nelson et al. ..2l9/6O 3,462,059 8/1969 Bauer et a1 ....228/5 3,498,5183/1970 Wheeler et al ..228/50 Primary Examiner-John F. CampbellAssistant Examiner-Robert J. Craig Attorney-R. Werlin [57] ABSTRACT Atool for use in welding together large diameter casing sections,particularly in forming liners for deep earth bores. The tool includesfluid pressure actuated expander assemblies operative to align thecasing sections, assure concentricity of the sections at the weld joint,and to position an expansible chill ring opposite the weld joint. Thetool also includes elements enabling pressure testing the welds, andhydraulic jacking means for moving the tool longitudinally of thecasing.

10 Claims, 18 Drawing Figures A55). A55)! A552 ASSZ A55)! RILIASE A B CD E SYSTJM OPEN Patented April 4, 1972 3,653,573

6 Sheets-Sheet 2 55 T 55 T 55 T SET SET HOLD HOL 0 H01 0 HOLD HOL 0OPE/V OPE N OPEN 0 OPE N OPEN ATTORNEY Patented April 4, 1972 3,653,573

6 Sheets-Sheet 3 Y i Mimi W Mal):

$2.4 Zia ATTORNEY Patented April 4, 1972 6 Sheets-Sheet 5 3 4 9 3 A 8 65 D 1/ r M (.4. w 1 wj fi fiif j E 0 L .I. M 71 w .6 w W 4 5 a o 5 4 9 La 1 A a qflj fifi j r. w E m 1? 8 m mw A m A W w N T gi E x w s p W w PE 4 a M4 My r J p ,r 7 m 1 w Patented April 4, 1972 3,653,573

6 Sheets-Sheet 6 C'IC'ERO 6'. BROWN INVliN'IT/R BY &

A T TORNEV CASING CENTRALIZER AND MANDREL FOR USE IN WELDING LARGEDIAMETER CASING Large diameter bore holes are currently being drilled togreat depths in the earth for various purposes, such as for mine shaftsand more particularly for placement of nuclear explosives in connectionwith tests conducted by the Atomic Energy Commission. Such bore holeswill often include sections of from to 6 feet in diameter and extendingvertically into the earth to depths of 5,000 feet or more. To seal offthe bore walls against entrance of formation fluids and to support themagainst cavity, steel casing must be run into the bore hole as a liner.

Such liners are preferably formed by welding successive sections of thepipe to the upper end of the casing string as it is inserted into thebore hole. The very large diameters and bulk and mass of the casingcreate difficult problems in accurately aligning the verticallysuspended added sections with the upper end of the casing in place inthe bore hole for purposes of welding the sections. This difficulty isaccentuated by the fact that such large diameter pipe sections arefrequently outof-round, so that it becomes very difficult to attain therequisite coaxial alignment and concentricity of the abutting ends ofthe sections which form the joint to be welded to assure a leak-tightweld. Also, pressure testing of the welds in place in the bore holes asthey are completed is another source of great difficulty under currentpractices.

It is a primary object, therefore, of the present invention to provide atool for use in welding large diameter casing sections, which obviatesdifficulties such as those enumerated above, by providing a structure bywhich the pipe ends to be joined are coaxially aligned, shaped tosubstantially full roundness, and are disposed in flush relation toenable accurate and tight welding.

Another object is the provision in a tool of the kind described ofelements for pressure testing the welds as they are completed, and ofhydraulic jack means for moving the tool longitudinally of the casingwithout requiring external hoisting equipment and for positioning thepressure testing elements in proper relation to the welds.

The tool, in accordance with one embodiment of this invention, comprisesa tubular support or mandrel, which carries longitudinally spaced upperand lower aligning assemblies. Each of these aligning assembliesincludes a plurality of fluid pressure-actuated, radially extensible andretractible shoes or slips, having substantially smooth faces adapted topress outwardly against the casing sections as to cause the ends thereofto assume a substantially true cylindrical shape, and to coaxially alignthe casing ends.

The longitudinal spacing of the assemblies is such that the upperassembly engages the casing section on one side of the joint, and thelower assembly includes slips having a length such as to span the jointbetween the sections so as to engage the immediately adjacent endportions of both pipe sections defining the joint. The latter assemblyincludes a circumferentially expansible segmented chill ring constructedof copper or the like, supported about the faces of the slips anddisposed for registration with the joint being welded. The chill ringfunctions to prevent bonding of the weld to the tool.

A first anchor assembly is mounted to the lower end of the tool andincludes fluid pressure actuated, radially extensible and retractiblepipe-gripping slips for anchoring the tool in the down-hole casingsection for locating the tool in operative position relative to thejoint to be welded.

For pressure testing the welds, the tool, as illustrated, has mountedbelow the first anchor assembly a tubular testing extension carryinglongitudinally spaced annular seals adapted to seal off between the tooland the casing at points above and below the weld to permit applicationof fluid pressure thereto. A second anchor assembly is carried by thelower end of the testing extension and includes a plurality of fluidpressure-actuated, radially extensible and retractible pipe-grippingslips for engagement with the casing wall. The two anchor assemblies areinter-connected by means enabling them to function as hydraulic jacks bywhich the entire tool may be raised and lowered in the casing asrequired for effectively positioning the tool therein, without requiringthe use of heavy duty external hoisting equipment.

The tool includes fluid pressure operated means for selectivelyactuating the several aligning, anchoring and testing assemblies inappropriate order, as required.

Various other objects and advantages of this invention will becomeevident from the following detailed description when read in conjunctionwith the accompanying drawing which illustrates a useful embodiment inaccordance with this invention.

In the drawing:

FIG. 1 is an elevational view of the tool inserted in the upper end of astring of casing in place in a bore hole;

FIG. 2 is a view similar to FIG. 1, showing a casing section emplacedover the tool in position to be welded to the string in the bore hole;

FIG. 3 is a longitudinal, cross-sectional view of the tool in theposition shown in FIG. 1 and showing the several pipe connections forsupplying actuating pressure fluid to the several fluidpressure-actuated elements of the tool;

FIGS. 4 to 13, inclusive, are fragmentary generally diagrammatic views,partly in section, illustrating the positions of the principal parts atvarious stages in the operation of the tool;

FIG. 14 is a cross-sectional view taken on line 14-14 of FIG. 3;

FIG. 14A is a fragment, on enlarged scale, of the structure shown inFIG. 14;

FIGS. 15 and 16 are cross-sectional views taken respectively on linesl5-l5 and 16-16 ofFlG. 3; and

FIG. 17 is a fragmentary sectional view of a detail of a typicalactuating cylinder.

Referring to the drawing, the tool comprises a tubular support member orbody 10, having an axial bore 11. Mounted about the exterior of body 10,moving downwardly from its upper end, or an upper aligning assembly,designated generally by the letter A, a lower aligning assembly,designated generally by the letter B, a first anchor turn, designatedgenerally by the letter C, a pressure testing assembly, designatedgenerally by the letter D, and a second anchor assembly designatedgenerally by the letter E.

The upper end of body 10 is covered by a cap 12 on the center of whichis mounted a shouldered hoisting neck 13, designed to be releasablygrasped by an overshot or gripping tool 14, of a generally conventionaldesign, which is suspended on a cable 15 attached to a block 16 whichis, in turn, supported on a hoisting frame 17 adapted to be raised andlowered by any conventional hoisting means, not shown, but preferablyhydraulic jack means, because of the great weights which may beinvolved.

As best seen in FIG. 3, aligning assembly A includes an expander 18secured about the upper end of body 10 and having a downwardly andinwardly tapering, conical surface 19, about which is arranged aplurality of angularly spaced slips 20 having generally smooth externalfaces 21 defining cylindrical segments and having tapering inner faces22 cooperating with expander surface 19 to produce radial extension andretraction of the slips in response to longitudinal movement thereofrelative to expander 18.

The set of slips 20 is mounted for limited radial movement in an annularcage 23 provided with an inwardly turned retainer lip 24 receivable incooperating grooves 24a in the slip shanks for connecting the slips tothe cage while cooperating with the slips to permit the necessary degreeof radial movement thereof. A plurality of angularly spaced verticallydisposed cylinders 25 are fixedly mounted about the exterior of body 10beneath cage 23, each cylinder being provided with a piston 26 attachedthrough the upper end of the cylinder and is secured to cage 23. Withthis arrangement it will be evident that reciprocation of the pistonswill raise and lower cage 23 whereby to move the set of slips 20 intoand out of expansive engagement with expander 18.

to a piston rod 27 which extends Each of the cylinders 25 is providedwith upper and lower ports 28 and 29, respectively, on opposite sides ofpiston 26 to function alternately as inlets and outlets for pressurefluids supplied through related header branch pipes 30 and 31,respectively, which, in turn, connect to valved conduits 32 and 33,respectively, suitably arranged in bore 11 and extending to the exteriorthereof through cap 12.

Lower aligning assembly B includes an annular expander 35 secured aboutthe exterior. of body below expander assembly A and having a downwardlyand inwardly tapering, generally conical surface 36. A plurality ofangularly spaced slips 37 is arranged about expander 35. Slips 37, whichare substantially longer than slips 20, have generally smooth externalfaces 38, defining generally cylindrical segments, and have taperinginner faces 39 cooperating with expander surface 36 to produce radialextension and retraction of the slips in response to longitudinalmovement thereof relative to expander 35.

As in the case of aligning assembly A, slips 37 are mounted for limitedradial movement in an annular cage 40 provided with an inwardly turnedretainer lip 41 receivable in grooves 41a for connecting the slips tothe cage while cooperating with the slips to permit the necessary extentof radial movement thereof.

A plurality of angularly spaced vertically disposed cylinders 42, likecylinders 25, are fixedly mounted about the exterior of body 10 beneathcage 40, each cylinder being provided with a piston 43 attached to apiston rod 44 which extends through the upper end of cylinder 42 and issecured to cage 40. Reciprocation of pistons 43 will raise and lowercage 40 whereby to move slips 37 into and out of expansive engagementwith expander 35.

Each of the cylinders 42 is provided with upper and lower ports 45 and46, respectively, on opposite sides of piston 43, to functionalternately as inlets and outlets for pressure fluids supplied throughrespective header branch pipes 47 and 48. Branch pipes 47 are connectedto conduit 32, while branch pipes 48 are connected to a valved conduit49 disposed in bore 11 and extending to the exterior thereof through cap12.

Seated in theexterior faces of slips 37 is an annular segmented chillring 50, constructed of copper or other highly heat-conductive material.As best seen in FIGS. 14 and 14A, in which the thickness dimensions ofthe chill ring are greatly exaggerated for purposes of illustration, thechill ring consists of three concentric segmented rings of copper sheet,numbered 50a, 50b and 50c. The segments overlap and are secured to theslips and to each other in a manner, illustrated in the drawing, suchthat the chill ring will be caused to circumferentially expand andretract in accordance with the radial extension and retraction of thesupporting slips while of the slips in response to longitudinal movementthereof relative to expander 35 Slips 53 are mounted for limited radialmovement in an annular cage 56 provided with an inwardly turned retainerlip 57 receivable in grooves 57a for connecting the slips to the cagewhile cooperating with the slips to permit the necessary extent ofradially movement thereof.

A plurality of vertically disposed angularly spaced cylinders 58 isfixedly mounted about the exterior of body 10 beneath cage 56, eachcylinder being provided with a piston 59 attached to a piston rod 60which extends through the upper end of cylinder 58 and is secured tocage 56. As in the other assemblies, reciprocation of pistons 59 willraise and lower cage 56 whereby to move slips 53, respectively, into andout of expansive engagement with expander 51.

Each of cylinders 58 is provided with upper and lower ports 61 and 62,respectively, on opposite sides of piston 59 to function alternately asinlet and outlet ports for pressure fluid sup plied through respectiveheader branch pipes 63 and 64. Branch pipes 63 are connected to conduit32 while branch pipes 64 are connected to a valved conduit 65 disposedin bore 1 l and extending to the exterior thereof through cap 12.

Pressure testing assembly D includes a tubular extension sleeve 70secured to the lower end of body 10, the actual connection being madefor convenience about the lower ends of cylinders 58. Sleeve 70 hasmounted about the outer periphery thereof longitudinally spaced upperand lower seal elements 71-71 of any suitable and generally well knownform, disposed and dimensioned to sealingly engage the surrounding wallof a liner casing P when fluid pressure is exerted in the annular space72 defined between seal elements 71-71 and related portions of casing P.

Extension sleeve 70 is provided with longitudinally spaced upper andlower ports 73 and 74, respectively, communicating with annular space 72and connected respectively to valved conduits 75 and 76 extendingupwardly in bore 11 through cap 12. A bottom plate 77 is connectedacross the lower end of extension sleeve 70.

Second anchor assembly E includes a tubular body 80 having a top plate81 closing the upper end thereof. An annular expander 82 is securedabout the upper end of body 80 and has a downwardly and inwardlytapering conical surface 83 about which is arranged a plurality ofangularly spaced slips 84 having toothed external faces 85 and taperinginner faces 86 cooperating with expander surface 83 to produce radialextension and retraction of the slips in response to longitudinalmovement thereof relative to expander 82. The set of slips 84 is mountedfor limited radial movement in an annular cage 87 provided with aninwardly turned retainer lip 88 receivable in cooperating grooves 88a inthe slip shanks for connecting the slips to the cage while cooperatingwith the slips to permit the necessary degree of radial movementthereof. A plurality of angularly spaced, vertically disposed cylinders89 are fixedly mounted about the exterior of body 80 beneath cage 87,each cylinder being provided with a piston 90 attached to a piston rod91which extends through the upper end of the cylinder and is secured tocage 87. As in the other assemblies, reciprocation of pistons 90 willraise and lower cage 87 whereby to move slips 84 into and out ofexpansive engagement with expander 84.

Each cylinder 89 is provided with upper and lower ports 92 and 93,respectively, on opposite sides of piston 90 to function alternately asinlet and outlet ports for pressure fluid supplied via the respectiveheader branch pipes 94a and 95a through the respective valved conduits94 and 95 which extend through plates 81 and 77 and thence upwardlythrough cap 12 to the exterior of the tool. Conduits 94 and 95 areprovided with extensible coupling sections 96 and 97, respectively, ofappropriate length and design to accommodate longitudinal movement ofbody 80 and assembly E relative to body 10 and its supported structure,for purposes to be more fully described hereinafter.

Mounted centrally on the upper face of plate 77 is an elongate cylinder98 closed at its upper end by a head 99. A piston 100 is mounted forreciprocation in cylinder 98 and is connected to a piston rod 101 whichextends slidably downwardly through plate 77 and is secured to plate 81and thereby to body 80 and second anchor assembly E. Cylinder 98 isprovided with upper and lower ports 102 and 103, respectively, onopposite sides of piston 100 to function alternately as inlet and outletports for pressure fluid supplied through the respective valved conduits104 and 105 which extend upwardly in bore 11 through cap 12 to theexterior of the tool. Cylinder 98 and piston 100 are arranged tofunction as a hydraulic jack cooperating with the upper and lower anchorassemblies for raising and lowering the tool inside the casing forpurposes to be described subsequently.

The upper ends of the several valved conduits projecting above cap'12are provided with conventional connectors 106 FIG. 2) for releasablyconnecting the several conduits to flexible supply pipes, designatedcollectively by the letter I-I(FIGS.

land 2). The supply pipes H are suitably supported on block 16 andextend to a supply manifold and operating console, designated generallyby the letter M, by means of which pressure fluid may be selectivelydirected into and vented from any of the several valved conduits, asrequired in the course of operation of the tool and as will be describedhereinafter.

It will be understood that the manifold and operating consolearrangement may be of any suitable and well known construction to enablethe selective movement of pressure fluid to and from the variousassemblies, as required, and the details thereof do not form a part ofthis invention.

OPERATION OF THE TOOL As seen in FIG. 1 and diagrammatically in FIG. 4,the tool is shown in place in the upper end of a casing section P, whichconstitutes the upper end of the casing string already in place in thewell bore W and supported on a foundation block F disposed on thesurface of the earth by means of cleats K secured about the exterior ofthe casing section adjacent its upper end. It may be assumed forpurposes of this description, that in the position illustrated in FIGS.1 and 4, the lowering of the casing string with the uppermost section Pin place has been completed and in position preparatory for theconnection of another section to the casing string. At this stage, upperanchor assembly C will be in its expanded position, anchoring the toolto casing section P, while lower anchor assembly E will be retracted asare aligning assemblies A and B. In order to hold slips 53 in theirexpanded engaged position, fluid will have been supplied to cylinder 58through conduit 65 and the valves in these conduits shut off to retainthe pressure in the cylinders. Thereupon, the group of supply pipes Hwill be disconnected from the several conduits and overshot 14 releasedfrom neck 13. Hoisting frame 17 may then be elevated and placed aboutthe upper end of a section P,(FIG. 2), to be attached to the upper endof casing section P. As illustrated, secti'on P, is provided with theexterior cleats K, by means of which the section may be suspended inhoist frame 17. When section P, is in place in the hoist frame, thegroup of supply pipes H will be dropped through the bore thereof andreconnected to the several valved conduits, whereupon section P, will belowered over the upper end of the tool until the scarfed lower end S ofsection P is in abutting relation to the upper end of casing P. Pressurefluid will now be supplied through pipes 33 and 49 to the respectivecylinders 25 and 42 to actuate the respective sets of aligning slipsmoving them upwardly and outwardly over the respective expanders l8 and34(FIG. 5). Any fluid above the respective pistons will be evacuatedthrough conduits 32. In this position of the tool, as illustrated, itwill be seen that upper aligning assembly A, particularly slips 20, willbe well above the joint J defined between the upper end of casing P andscarfie d end S. Slips 37 of lower aligning assembly B will bepositioned across joint J so as to extend above and below joint J tospan the same and to place chill ring 50 directly opposite the joint.

When the aligning slips of assemblies A and B are thus actuated, theywill apply radial and circumferential pressure about the interior of theadjacent ends of the pipe defining joint J, so as to force theseadjacent portions of the casing into substantially true roundness and inconcentric alignment with each other at the joint. Welding of the jointmay now be accomplished in any conventional manner.

At the time the tool is positioned for purposes of alignment andcompleting the welding of the joint, lower anchor assembly E will be inthe released condition, as seen in FIGS. 1, 4 and 5, and body 80carrying anchor assembly E will be in its upwardly retracted positionrelative to testing assembly D and the main body of the tool.

Anchor assemblies C and E may now be operated cooperatively throughhydraulic jacking procedures to raise the entire tool inside the casingto position it either for pressure testing the welded joints or forraising the tool to the initial position seen in FIGS. 1 and 2preparatory to connection of another section of casing. By employingsuch procedures, the hoisting mechanism is relieved of much of the largeloads constituted by the necessarily massive construction of the tool.FIGS. 6 to 13 illustrate stages in such operations of the tool.

To use the tool for pressure testing the weld at joint J, starting withthe parts in the positions in FIG. 5, both aligning assemblies and upperanchor assembly C are in set position while anchor assembly E is in theunset or retracted position both with respect to the casing and withrespect to the main body of the tool.

Fluid pressure will now be applied through conduit 95 to actuateslips-84 so as to move them into gripping engagement with casing P(FIG.6). With the lower anchor assembly E now set, pressure is relieved fromboth aligning assemblies A and B and upper anchor assembly C by ventingthe pressure from their respective sets of cylinders through the commonconduit 32 (FIG. 7). Fluid pressure will now be applied through conduit102 into cylinder 98 above piston 100 (FIG. 8). Since the latter is nowsecured to casing P by means of the slips 84, the pressure in cylinder98 will raise the entire main body of the tool, including testingassembly D, upwardly in the casing for the full length of the stroke ofpiston 100 which, for the purpose of this description, it will beassumed is sufficient to position seal elements 71,71 on opposite sidesof joint J(FIG. 8). Pressure fluid will now be re-applied throughconduit 65 to the actuating cylinders of upper anchor assembly C,actuating slips 53 into pipe-gripping engagement with casing P,(FIG. 9),so that the tool is now effectively anchored to the casing on oppositesides of joint J. Pressure fluid for testing joint J will now beintroduced into annular space 72 between the seal elements via either ofconduits 75 or 76, whichever may be selected as the inlet conduit forthis purpose, the other being shut-off in order to allow the pressure tobuild up inside annular space 72 between the seal elements and therebyapply the desired testing pressure to joint J, as illustrated in FIG.10.

When testing of the weld has been completed, the pressure fluid isvented from annular space 72 and operations are continued in order toraise the entire tool to the upper end of section P, to the positionshown in FIG. 1 preparatory to the addition of another section of thecasing. This raising operation employs the hydraulic jacking elements,as illustrated particularly in FIGS. 11, 12 and 13. First, pressure isrelieved from lower anchor assembly E through conduit 94, allowingretraction of slips 84 while actuating pressure is maintained on upperanchor assembly C to hold slips 53 in casing-gripping engagement. Withlower anchor assembly E released, fluid pressure is now directed intocylinder 98 under piston 100 through conduit 103 to raise body carryingthe now released anchor assembly E upwardly relative to the main bodyofthe tool (FIG. 12) to the same position as seen in FIG. 4. In the nextstage, shown in FIG. 13, hydraulic pressure is reapplied through conduitto cylinders 89 of lower anchor assembly E to reset slips 84 in thecasing. When that is done, the pressure may be relieved from upperanchor assembly C to release slips 53 for return to the position shownin FIG. 8, whereupon pressure fluid may again be applied to cylinder 98as in FIG. 8 to raise the main body of the tool by a lengthcorresponding to a stroke of piston 100. This sequence of operations maythen be repeated until the upper portion of the tool has been returnedto the initial position illustrated in FIG. 1 preparatory to theinstallation of the next section of casing, in the manner previouslydescribed.

As will be evident, manifold or console M will be arranged in a knownmanner so that by appropriate manipulation of the controls employedtherein the operator may selectively direct pressure fluid to and fromthe various assemblies in any desired sequence required for actuatingthe aligning assemblies and the anchor and pressure testing assembliesto accomplish the several functions heretofore described.

It will be evident from the foregoing that the tool may be made tofunction entirely satisfactorily as a welding mandrel, employing onlyaligning assemblies A and B and upper anchor assembly C. This isparticularly the case where it may be found unnecessary to pressure testthe welds and where it may be found unnecessary or undesirable to employthe hydraulic jacking pressure to move the tool inside the casing.However, both the pressure testing assembly and the lower anchorassembly will generally be found to be highly useful as a part of thecomplete tool.

It will be evident that various modifications and alterations may bemade in the details of the illustrative embodiment within the scope ofthe appended claims but without departing from the spirit of thisinvention.

What I claim and desire to secure by Letters Patent is:

1. A centralizing mandrel for use in welding large diameter casing,comprising:

a. a tubular support member insertible in a casing across a joint to bewelded;

b. a first annularly expansible aligning assembly mounted on saidsupport member for movement into and out of expansive engagement withthe adjacent portions of the casing sections defining said joint;

c. a second annularly expansible aligning assembly mounted on saidsupport member for movement into and out of expansive engagement withthe casing section on one side of said joint at a point longitudinallyspaced from said joint, said assemblies cooperating when expanded tocoaxially align said casing portions in concentric substantially flushrelation;

d. a radially expansible anchor assembly mounted on said support memberfor movement into and out of anchoring engagement with the casingsection on the opposite side of said joint; and

e. fluid pressure-operated means for selectively actuating the severalassemblies.

2. A mandrel according to claim 1 including a segmented chill ringmounted about said first aligning assembly movable thereby intoconcentric registration with said joint upon expansion of said aligningassembly.

3. A mandrel according to claim 1, including a pressuretesting assemblycarried by said support member below said anchor assembly, said testingassembly comprising:

a. a tubular sleeve;

b. longitudinally spaced annular expansible seal elements mounted aboutsaid sleeve for sealing engagement with the surrounding casing anddefining therewith a pressure chamber; and

c. means for introducing pressure fluid into said chamber for actuatingsaid seal elements.

4. A mandrel according to claim 3, including a segmented chill ringmounted about said first aligning assembly movable thereby intoconcentric registration with said joint upon expansion of said aligningassembly.

5. A mandrel as defined in claim 1, including:

a. a second radially expansible anchor assembly mounted on a secondtubular support member for movement into and out of anchoring engagementwith the surrounding casing at a point spaced from said first anchorassembly;

b. fluid pressure-actuated jack means connecting said first and secondsupport members for relative axial movement; and

. said fluid pressure-operated means including means for selectivelyactuating said second anchor assembly and said jack means in cooperationwith said first anchor assem bly whereby to enable movement of saidmandrel longitudinally in said casing.

6. A mandrel as defined in claim 5, including a segmented chill ringmounted about said first aligning assembly movable thereby intoconcentric registration with said joint upon expansion of said firstaligning assembly.

7. A mandrel according to claim 5, including a pressuretesting assemblycarried by said support member between said anchor assemblies, saidtesting assembly comprising:

a. a tubular sleeve secured to said support member;

b. longitudinally spaced annular expansible seal elements mounted aboutsaid sleeve for sealing engagement with the surrounding casing anddefining therewith a pressureconfining chamber; and

0. means for introducing pressure fluid into said chamber.

d. said testing assembly being movable with said mandrel by saidcooperation between said anchor and jacking assemblies to a positionspanning said joint.

8. A mandrel according to claim 1, wherein each of said aligningassemblies comprises:

a. an expander ring;

b. a plurality of angularly spaced slips having substantially smoothcasing-engaging faces disposed about said expander ring for radialexpansion and contraction in response to longitudinal movement relativeto said expander ring; and

c. fluid pressure-actuated means for effecting said longitudinalmovement.

9. A mandrel according to claim 5, wherein each of said aligningassemblies comprises:

a. an expander ring;

b. a plurality of angularly spaced slips having substantially smoothcasing-engaging faces disposed about said expander ring for radialexpansion and contraction in response to longitudinal movement relativeto said expander; and

c. fluid pressure-actuated means for effecting said longitudinalmovement.

10. A centralizing mandrel for use in welding large diameter casing,comprising;

a. a tubular support member insertible in a casing across a joint to bewelded;

b. a first annularly expansible aligning assembly mounted on saidsupport member for movement into and out of expansive engagement withthe adjacent portions of the casing sections defining said joint;

c. a second annularly expansible aligning assembly mounted on saidsupport member for movement into and out of expansive engagement withthe casing section on one side of said joint at a point longitudinallyspaced from said joint, said assemblies cooperating when expanded tocoaxially align said casing portions in concentric substantially flushrelation;

(1. a first radially expansible anchor assembly mounted on said supportmember. for movement into and out of anchoring engagement with thecasing section on the opposite side of said joint;

c. a pressure testing assembly carried by the support member below saidfirst anchor assembly and carrying means for sealing off between thesupport member and the casing at points above and below said joint whenpositioned opposite the joint;

a second radially expansible anchor assembly mounted on a second tubularsupport member for movement into and out of anchoring engagement withthe surrounding casing at a point spaced from said first-mentionedanchor assembly and below said testing assembly;

g. a fluid pressure actuated jack assembly connecting said first andsecond support members for relative axial movement; and

h. fluid pressure-operated means for selectively actuating the severalassemblies in a predetermined order.

1. A centralizing mandrel for use in welding large diameter casing,comprising: a. a tubular support member insertible in a casing across ajoint to be welded; b. a first annularly expansible aligning assemblymounted on said support member for movement into and out of expansiveengageMent with the adjacent portions of the casing sections definingsaid joint; c. a second annularly expansible aligning assembly mountedon said support member for movement into and out of expansive engagementwith the casing section on one side of said joint at a pointlongitudinally spaced from said joint, said assemblies cooperating whenexpanded to coaxially align said casing portions in concentricsubstantially flush relation; d. a radially expansible anchor assemblymounted on said support member for movement into and out of anchoringengagement with the casing section on the opposite side of said joint;and e. fluid pressure-operated means for selectively actuating theseveral assemblies.
 2. A mandrel according to claim 1 including asegmented chill ring mounted about said first aligning assembly movablethereby into concentric registration with said joint upon expansion ofsaid aligning assembly.
 3. A mandrel according to claim 1, including apressure-testing assembly carried by said support member below saidanchor assembly, said testing assembly comprising: a. a tubular sleeve;b. longitudinally spaced annular expansible seal elements mounted aboutsaid sleeve for sealing engagement with the surrounding casing anddefining therewith a pressure chamber; and c. means for introducingpressure fluid into said chamber for actuating said seal elements.
 4. Amandrel according to claim 3, including a segmented chill ring mountedabout said first aligning assembly movable thereby into concentricregistration with said joint upon expansion of said aligning assembly.5. A mandrel as defined in claim 1, including: a. a second radiallyexpansible anchor assembly mounted on a second tubular support memberfor movement into and out of anchoring engagement with the surroundingcasing at a point spaced from said first anchor assembly; b. fluidpressure-actuated jack means connecting said first and second supportmembers for relative axial movement; and c. said fluid pressure-operatedmeans including means for selectively actuating said second anchorassembly and said jack means in cooperation with said first anchorassembly whereby to enable movement of said mandrel longitudinally insaid casing.
 6. A mandrel as defined in claim 5, including a segmentedchill ring mounted about said first aligning assembly movable therebyinto concentric registration with said joint upon expansion of saidfirst aligning assembly.
 7. A mandrel according to claim 5, including apressure-testing assembly carried by said support member between saidanchor assemblies, said testing assembly comprising: a. a tubular sleevesecured to said support member; b. longitudinally spaced annularexpansible seal elements mounted about said sleeve for sealingengagement with the surrounding casing and defining therewith apressure-confining chamber; and c. means for introducing pressure fluidinto said chamber, d. said testing assembly being movable with saidmandrel by said cooperation between said anchor and jacking assembliesto a position spanning said joint.
 8. A mandrel according to claim 1,wherein each of said aligning assemblies comprises: a. an expander ring;b. a plurality of angularly spaced slips having substantially smoothcasing-engaging faces disposed about said expander ring for radialexpansion and contraction in response to longitudinal movement relativeto said expander ring; and c. fluid pressure-actuated means foreffecting said longitudinal movement.
 9. A mandrel according to claim 5,wherein each of said aligning assemblies comprises: a. an expander ring;b. a plurality of angularly spaced slips having substantially smoothcasing-engaging faces disposed about said expander ring for radialexpansion and contraction in response to longitudinal movement relativeto said expander; and c. fluid pressure-actuated means for effectingsaid longitudinal movement.
 10. A centralizing mandrel for use inwelding large diameter casing, comprising; a. a tubular support memberinsertible in a casing across a joint to be welded; b. a first annularlyexpansible aligning assembly mounted on said support member for movementinto and out of expansive engagement with the adjacent portions of thecasing sections defining said joint; c. a second annularly expansiblealigning assembly mounted on said support member for movement into andout of expansive engagement with the casing section on one side of saidjoint at a point longitudinally spaced from said joint, said assembliescooperating when expanded to coaxially align said casing portions inconcentric substantially flush relation; d. a first radially expansibleanchor assembly mounted on said support member for movement into and outof anchoring engagement with the casing section on the opposite side ofsaid joint; c. a pressure testing assembly carried by the support memberbelow said first anchor assembly and carrying means for sealing offbetween the support member and the casing at points above and below saidjoint when positioned opposite the joint; f. a second radiallyexpansible anchor assembly mounted on a second tubular support memberfor movement into and out of anchoring engagement with the surroundingcasing at a point spaced from said first-mentioned anchor assembly andbelow said testing assembly; g. a fluid pressure actuated jack assemblyconnecting said first and second support members for relative axialmovement; and h. fluid pressure-operated means for selectively actuatingthe several assemblies in a predetermined order.